The present invention relates generally to electric drives and is useful in direct current brushless motors.
It is desirable to have small overall dimensions and high reliability in electric drives. These requirements are especially important for electric drives operating in cooling systems with blower and heatsink for regulating the temperature of electronic devices. The trend toward smaller and thinner electronic devices having faster processors renders traditional heat removal cooling systems inadequate. It is desirable that the electric drives of these systems be small, thin and efficient as well.
At the same time the electric drives should have high reliability, since the failure of the electric drives of said cooling systems could cause electronic devices to malfunction during use, or lead to premature device failure.
The best method for increasing the reliability of such systems is to incorporate redundancy of their parts. In particular, such electric drives often have (as described, for example, in the patent application WO No 94/14226) additional reserve stator windings, which work in case of failure of one or more of the main windings. Normally providing higher reliability by providing redundancy increases overall sizes of the electric drives.
Many types of electric drives comprise a magnetic rotor and a stator with coils wrapped about some cylindrical core are known, but such electric drives are not compact enough.
There is known an electric drive with coils wrapped about some ring-shape core, as described in U.S. Pat. No. 5,440,185. This device incorporates a magnetic rotor and a stator with coils wrapped about ring-shape disk.
There is known an electric drive described in U.S. Pat. No. 4,645,961, “Dynamoelectric machine,” composed of a magnetic rotor and a stator with the winding made as a cylindrically shaped ring, wherein said stator incorporates additional circumferentially placed printed circuit coils that form two coil layers made as parts of a common printed circuit board. Said coils of the different layers are electrically connected and form together a ring-shaped winding, the two said coil layers of which are separated by a layer of an electro-insulating material.
There is known an electric drive described in the patent application WO No 03/003547 A1 (PCT/U.S. Pat. No. 02/20224) “Brushless DC Electric Motor” composed of a magnetic rotor and a stator with two windings made as disk rings located around a common axis on opposite sides from the rotor, wherein each of said windings incorporates circumferentially placed printed circuit coils that form two coil layers made as parts of a common printed circuit board and located on opposite sides of an electro-insulating layer. Said coils of different layers are electrically connected, forming together a ring-shaped winding. Both windings are the main windings, and operate together during normal operation.
The above mentioned electric drives with ring-shaped windings are the most compact from all known electric drives. But reliability improvements realized without using additional reserved winding(s), as well as efficiency improvements, could additionally decrease the sizes of such devices.
It would be generally desirable to provide an electric drive that has higher reliability without using reserved windings. This would decrease device sizes and at the same time provide the benefit of higher efficiency that can yield higher rotation speed and the possibility of additional decreasing its overall sizes.